1. Field of the Disclosure
The present disclosure relates generally to fuser control in an electrophotographic imaging device, and particularly to an apparatus and methods for more effectively and efficiently controlling the fuser assembly of an imaging device.
2. Description of the Related Art
Alternating current (AC) line voltage and power quality across the world are not always within listed specifications and often vary considerably. This can be due to problems and shortcomings with the power grid or even with the power distribution inside a building. The voltage or power quality variation has a substantial impact on the operation of electrophotographic printing devices, and particularly on fuser temperature control and printer performance because fuser heater power changes dramatically with AC line voltage variation. Fuser heater power variations have been seen to cause a number of problems. For instance, excessive fuser heater power increases the likelihood of cracking of the fuser heater in the belt fuser. Low fuser heater power often leads to insufficient fusing of toner to sheets of media because the fuser heater cannot maintain suitable fusing temperature for acceptable toner fusing. When fusing temperatures cannot be maintained during a printing operation, the printer may stop printing altogether and issue an error, often leading to a disruption in work by those needing timely printed material. Significant fuser heater power variation also makes it difficult to predict the amount of time needed for a fuser to be ready for performing fusing during a print operation. Inaccurate prediction of such “fuser ready time” may cause poor toner fusing because media sheets enter into the fuser nip of the fuser assembly too early or arrive too late, oftentimes leading to the imaging device flagging an error and stopping the print job before completion. Further, sizeable power variations make it difficult to achieve relatively tight temperature control of the fuser heater. Sizeable variation in fuser heater temperature during a print operation has been seen to cause hot offset in which toner is undesirably transferred to the belt of the fusing assembly when fusing temperatures are too high, resulting in the transferred toner transferring back to the media sheet one belt revolution later. Further, toner that is fused at elevated temperatures oftentimes does not have a shiny appearance.
Still further, fusing toner at elevated temperatures can result in media sheets undesirably wrapping around the belt of the fuser assembly instead of exiting therefrom, thereby leading to a media jam condition and a further disruption in printing.
To address the above challenges, some existing imaging devices use the time it takes for a fuser heater to be warmed to fusing temperatures to predict the AC line voltage. However, such predictions are often inaccurate due to the fuser heater warm up time being influenced by other factors such as variation of initial fuser heater temperature prior to fuser heater warm up, fuser heater resistance distribution, variation in fuser heater thickness, the operation of the thermistor which is secured to the fuser heater, and the contact between the thermistor and fuser heater.
Further, existing algorithms for checking excessive fuser heater power are often executed only when the fuser heater temperature is very low, such as less than 50 degrees C. during power up of the imaging device or when the imaging device wakes up and/or exits from a sleep mode of operation.